The overall objective of this research project is the elucidation of the organization of genetic elements in the eukaryote chromosome concerned with the time specific and tissue specific regulation of gene activity during development. Specificially, we propose to induce, recover, and characterize high and low activity, time specific, and tissue specific regulator mutants in contiguous control elements of the gene for dopa decarboxylase (DDC) in Drosophila melanogaster. These contiguous regulator mutants will be subjected to high resolution mapping to establish that the lesions are in regions outside the structural element, to determine the positions of the cluster relative to one another. Studies on non-contiguous DDC regulator mutations and suppressors of contiguous regulator mutations will be initiated to identify those effector molecules which interact with control elements in the DDC structural gene. In addition, DDC specific DNA will be isolated and amplified in recombinant plasmids. Wild type DNA and DNA from regulator mutants will then be investigated in an effort to elucidate the nature of the controlling elements.